Fetal nasal bone length and Down syndrome during the   second trimester in a Chinese population.
OBJECTIVE
The purpose of the present study was to build a database of reference ranges of fetal nasal bone length (NBL) in a Chinese population. The accuracy rate of detecting Down syndrome was also analyzed using fetal NBL as a marker.


METHODS
The control group of fetuses included 342 normal singleton pregnancies with no chromosomal or congenital anomalies. The present study was a cross-section study and the control group was used to construct percentile values of NBL from 13 to 29 gestational weeks of age. Two-dimensional ultrasonography was used for the nasal bone studies. Measurements of NBL were collected and each fetus contributed a single value to the reference sample. During the study period, 14 fetuses with Down syndrome were examined. Measurement of fetal NBL was made during amniocentesis, with gestational age ranging from 13 to 19 weeks.


RESULTS
From 342 normal fetuses with gestational age ranging from 13 to 29 weeks, reference ranges of NBL were constructed. The reference ranges were constructed from the 100(1 - p)% reference range: Y +/- Zp x square root sigma 2, where Y = 25 - exp(3.58 - 0.044 x t + 0.0006 x t2), with Y being the fitted mean of regression model and t being gestational age (weeks). Using fetal NBL, the regression model was Pr(Down syndrome) = exp(W)/ [1 + exp(W)], where W = 0.62-4.80 x NBL (multiples of the median) in predicting Down syndrome. Fetal NBL was found to have a sensitivity and specificity of 0.78 and 0.78, respectively, in predicting Down syndrome in the second trimester of pregnancy.


CONCLUSIONS
Fetal NBL measurement can provide a simple and useful algorithm to predict Down syndrome during the second trimester of pregnancy.
Hung
Jeng-Hsiu
JH
Department of Obstetrics and Gynecology, Buddhist Tzu Chi General Hospital, Taipei branch, 289 Jianguo Road, Xindian City, Taipei 231, Taiwan. jhhung@tzuchi.com.tw
Fu
Chong Yau
CY
Chen
Chih-Yao
CY
Chao
Kuan-Chong
KC
Hung
Jamie
J
D000293:Adolescent; D000328:Adult; D000465:Algorithms; D002681:China; D003430:Cross-Sectional Studies; D004314:Down Syndrome / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000235:genetics; D005260:Female; D006801:Humans; D009295:Nasal Bone / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012016:Reference Values; D014463:Ultrasonography